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Tele-phone man · August 2nd, 2007, 01:41 AM

quote:
There is nothing untrue about my statements. Experienced ears will know from listening how this amp does the OD and the reverb. Check the schematic
and you will find the chips and diodes in the drive section and in the reverb section.
Whether or not one can hear the results of this type of circuit is another question.
AS to the statement about the number of preamp tubes that are necessary to achieve all-tube processing with OD and reverb, there is nothing untrue about it. If it were possible to do tube OD and reverb with 3 preamp tubes, manufacturers would do so instead of using chips and diode(solid state devices). The first amp of this type that I encountered was the JCM 900 high gain dual reverb. My tech at the time and a talented soundman (Point Blank, Reba MacIntyre national tour, etc) was running sound for a rock group in a club here. The guitarist was raving about his new Marshall. This was when the JCM 900's first came out. He said it was the beest tube amp that he had ever played. My friend noted that it didn't sound like an all tube amp. They 'discussed' the matter. My tech said that he would put money that the amp did OD and reverb through TL072 IC's. In fact, those are the chips that drive those functions. There are 9 or 13..I forget which...of them in the amp. Some do switching, but the OD and reverb are SS driven.
I have never seen an amp that processes reverb and OD through tubes that has leess than 5 preamp tubes.....Mesa, Rivera, etc. IF the amp has 3 preamp tubes and does OD and reverb, you can be assured even if you can't hear the solid state 'qualities' of these functions, that SS devices drive the OD and the reverb. In the HRD, you will see 2 4568's and some diodes in the Drive functions. It is true that the signal is routed from a tube to the SS devices that do the OD and then returns to a tube, but the OD is SS driven. In the reverb, you will see two TL072's.
I am not condemning this or any other amp for using the less expensive route to achieving these functions. I simply think that people who haven't heard the difference should know the difference....especially since they are sold on the 'all-tube' hype when the amp is marketed to them. It takes time and experience to hear the difference even without the misrepresentation.

Wally,

I have to side with Detuned on this one. While it's true that the JCM900 had clipping diodes in the signal path, it is also true that if you avoid the effects loop and the reverb circuit, the HRD amp signal path is ALL tube. The FETs are used purely as switches to bring some other components (primarily capacitors) into and out of the circuit. The diodes are used to keep the gate voltage on the FETs at the correct polarity. The same result could have been achieved with relays, but the cost would have been much higher. Neither the FETs nor the diodes are used as amplifiers or clippers in any way. You cannot "hear" them. This is a fact, not an opinion.

The next statement is my opinion: You cannot "hear" the op-amp in the effects loop. These circuits are extremely transparent, and if you really think that you can tell the difference between a well-designed solid-state buffered effects loop from a tube-driven effects loop, you are delusional. You may be fooling yourself, but don't believe for a moment you are fooling me. I've been around this game too long and have heard (and debunked) way too many unsubstantiated claims from tube snobs to be willing to listen to any universal statements such as the ones you've laid on us.

As Detuned said, if it sounds good, it is good. Some solid-state circuits sound fantastic, some tube circuits sound like ****, and vice-versa. Ever try a Pritchard amp? They will make you question all your assumptions about the inherent superiority of tube amps.

August 2nd, 2007, 01:41 AM	#48 (permalink)
Tele-phone man TDPRI Member Join Date: Sep 2006 Location: Asheville, NC Age: 45 Posts: 67	quote: There is nothing untrue about my statements. Experienced ears will know from listening how this amp does the OD and the reverb. Check the schematic and you will find the chips and diodes in the drive section and in the reverb section. Whether or not one can hear the results of this type of circuit is another question. AS to the statement about the number of preamp tubes that are necessary to achieve all-tube processing with OD and reverb, there is nothing untrue about it. If it were possible to do tube OD and reverb with 3 preamp tubes, manufacturers would do so instead of using chips and diode(solid state devices). The first amp of this type that I encountered was the JCM 900 high gain dual reverb. My tech at the time and a talented soundman (Point Blank, Reba MacIntyre national tour, etc) was running sound for a rock group in a club here. The guitarist was raving about his new Marshall. This was when the JCM 900's first came out. He said it was the beest tube amp that he had ever played. My friend noted that it didn't sound like an all tube amp. They 'discussed' the matter. My tech said that he would put money that the amp did OD and reverb through TL072 IC's. In fact, those are the chips that drive those functions. There are 9 or 13..I forget which...of them in the amp. Some do switching, but the OD and reverb are SS driven. I have never seen an amp that processes reverb and OD through tubes that has leess than 5 preamp tubes.....Mesa, Rivera, etc. IF the amp has 3 preamp tubes and does OD and reverb, you can be assured even if you can't hear the solid state 'qualities' of these functions, that SS devices drive the OD and the reverb. In the HRD, you will see 2 4568's and some diodes in the Drive functions. It is true that the signal is routed from a tube to the SS devices that do the OD and then returns to a tube, but the OD is SS driven. In the reverb, you will see two TL072's. I am not condemning this or any other amp for using the less expensive route to achieving these functions. I simply think that people who haven't heard the difference should know the difference....especially since they are sold on the 'all-tube' hype when the amp is marketed to them. It takes time and experience to hear the difference even without the misrepresentation. Wally, I have to side with Detuned on this one. While it's true that the JCM900 had clipping diodes in the signal path, it is also true that if you avoid the effects loop and the reverb circuit, the HRD amp signal path is ALL tube. The FETs are used purely as switches to bring some other components (primarily capacitors) into and out of the circuit. The diodes are used to keep the gate voltage on the FETs at the correct polarity. The same result could have been achieved with relays, but the cost would have been much higher. Neither the FETs nor the diodes are used as amplifiers or clippers in any way. You cannot "hear" them. This is a fact, not an opinion. The next statement is my opinion: You cannot "hear" the op-amp in the effects loop. These circuits are extremely transparent, and if you really think that you can tell the difference between a well-designed solid-state buffered effects loop from a tube-driven effects loop, you are delusional. You may be fooling yourself, but don't believe for a moment you are fooling me. I've been around this game too long and have heard (and debunked) way too many unsubstantiated claims from tube snobs to be willing to listen to any universal statements such as the ones you've laid on us. As Detuned said, if it sounds good, it is good. Some solid-state circuits sound fantastic, some tube circuits sound like ****, and vice-versa. Ever try a Pritchard amp? They will make you question all your assumptions about the inherent superiority of tube amps.